JP2015044149A - Flocculation treatment method, flocculation treatment device and water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flocculation treatment method, a flocculation treatment device and a water treatment apparatus where an aqueous solution sufficiently dissolved with a flocculant is added into water to be treated and highly efficient flocculation treatment can be realized.SOLUTION: A flocculation treatment device comprises: a flocculant aqueous solution storage tank 1 with an agitator 5 to store a flocculant aqueous solution; a particle size distribution measuring device 50 to measure the particle size distribution of the flocculant aqueous solution in the flocculant aqueous solution storage tank 1; a flocculation tank 11 to form an aggregate by mixing the water to be treated with the added flocculant aqueous solution; an aggregate removal part 9 to remove the aggregate from aggregate-containing treatment water; and a controlling unit 6 to control the agitator 5 so that a median diameter in the particle size distribution of the flocculant aqueous solution based on the measured particle size distribution is 1.0 μm or less.

Description

  The present invention relates to an aggregating method, an aggregating apparatus, and a water treatment apparatus equipped with the aggregating apparatus, in which an aggregating agent is added to water to be treated to form an aggregate.

  As for water purification technology for producing drinking water and irrigation water from natural water such as river water, chemical methods such as a coagulation sedimentation method and physical methods such as a sand filtration method have been considered.

  On the other hand, in recent years, water shortages have become an issue in countries around the world, including the Middle East and Asia. In order to cope with this, seawater desalination technology for desalinating seawater to produce drinking water and irrigation water has attracted attention and has been put into practical use. As a seawater desalination method, an evaporation method for obtaining fresh water by heating seawater to evaporate water and cooling steam has been performed. However, since the evaporation method is inferior in energy efficiency and costly, a more efficient method is desired. At present, a reverse osmosis method in which fresh water is obtained by desalting by membrane filtration using a reverse osmosis membrane (RO membrane) is becoming mainstream. In order to prevent contamination of the RO membrane, it is necessary to perform an appropriate pretreatment for removing turbid substances, organic substances and the like before passing seawater through the RO membrane. As a pretreatment method, as in the case of water purification treatment, membrane filtration using an ultrafiltration membrane (UF) or microfiltration membrane (MF), use of an adsorbent such as activated carbon, use of a flocculant, and the like are being studied.

  Typical flocculants in wastewater treatment and water purification are inorganic flocculants using polyvalent metal ions (cations) such as polyaluminum chloride (PAC) and iron chloride, and water-soluble polyvalent ions. There are polymer flocculants using polymers (polymer flocculants) and the like. These remove the charged impurities contained in the water by coagulation precipitation. In addition, when a sufficient effect cannot be obtained even if one of the inorganic and organic flocculating agents is applied, the flocculating effect may be enhanced by using the inorganic and organic flocculating agents in combination. is there.

Patent Document 1 describes an apparatus that uses an aqueous solution when a polymer flocculant is used, and discloses an apparatus that has a mechanism for measuring the concentration of a dissolved aqueous polymer flocculant solution.
Patent Document 2 discloses a method for agglomerating impurities in which an organic flocculant and an inorganic flocculant are added simultaneously or in this order when removing impurities in water such as seawater and river water, and pH adjustment is performed. .

  Patent Document 3 discloses a boron removal method of adding a flocculant for boron removal after adjusting pH using a pH adjuster in seawater desalination.

JP 2002-136809 A JP 2008-264723 A JP 10-225682 A

  However, none of Patent Documents 1 to 3 has a function of measuring the particle size distribution in the aqueous flocculant solution and cannot determine whether the flocculant is sufficiently dissolved in the aqueous solution. Therefore, if the flocculant is a polymer flocculant, if an aqueous flocculant solution that is insufficiently dissolved is added to perform the flocculant treatment, the flocculant efficiency is reduced and the flocculant is consumed more than necessary.

  The present invention provides a coagulation treatment method, a coagulation treatment apparatus and a water treatment apparatus capable of realizing a highly efficient coagulation treatment by adding a sufficiently dissolved coagulant aqueous solution to the water to be treated.

  In order to solve the above problems, the present invention adds one or more aqueous flocculant solutions to the water to be treated containing impurities to form agglomerates, and removes the formed agglomerates. An aggregating treatment method for removing impurities, wherein the median diameter in the particle size distribution of the aggregating agent aqueous solution is 1.0 μm or less.

  The present invention also includes a flocculant aqueous solution storage tank that includes a stirrer and stores a flocculant aqueous solution, a particle size distribution measuring device that measures the particle size distribution of the flocculant aqueous solution in the flocculant aqueous solution storage tank, and water to be treated. And an aggregating tank that mixes the aqueous flocculant solution to be added to form an aggregate, an aggregate removal unit that removes the aggregate from the treated water containing the aggregate, and the particle size distribution based on the measured particle size distribution A controller for controlling the agitator is provided so that the median diameter in the particle size distribution of the flocculant aqueous solution is 1.0 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the coagulant | flocculant aqueous solution fully melt | dissolved can be added to to-be-processed water, and the coagulation process method, coagulation process apparatus, and water treatment apparatus which can implement | achieve highly efficient coagulation process can be provided.

  For example, when a polymer flocculant is used as the flocculant, it can be uniformly dispersed in the water to be treated, and the flocculation treatment efficiency can be improved. Therefore, chemicals in the flocculation treatment process can be reduced, and the operating cost of the water treatment apparatus can be reduced. Is possible.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a whole block diagram of the water treatment apparatus which has the aggregation process part which concerns on this invention. It is another whole block diagram of the water treatment apparatus which has a coagulation process part which concerns on this invention. It is another whole block diagram of the water treatment apparatus which has a coagulation process part which concerns on this invention. It is another whole block diagram of the water treatment apparatus which has a coagulation process part which concerns on this invention. It is a figure explaining the relationship between a particle size distribution and trapping of impurities. It is a figure explaining the relationship between the particle size distribution and treated water quality of each Example. It is a figure explaining the relationship between the particle size distribution of each comparative example, and a treated water quality. It is a figure which shows the relationship between an acidic sugar removal rate and the raise speed | rate of clogging (filtration pressure).

  Hereinafter, an aggregation treatment method, an aggregation treatment apparatus, and a water treatment apparatus according to an embodiment of the present invention will be described. The present invention is characterized in that the median diameter (d50) in the particle size distribution of the polymer flocculant aqueous solution used for the aggregation treatment is 1.0 μm or less. Here, the median diameter means a particle diameter in which the large side and the small side are equivalent when the powder is divided into two from a certain particle diameter, and is generally described as d50. By injecting the polymer flocculant aqueous solution in a state in which the particle diameter of the aqueous polymer flocculant solution is sufficiently small, the flocculant can be quickly and uniformly dispersed in the water to be treated, thereby enabling highly efficient flocculation. When the water to be treated is high-concentration salt water such as seawater, the pH of the flocculant aqueous solution is preferably made acidic (pH 2 or lower, preferably 1 or lower). This is due to the dissociated state of the flocculant, and will be described by taking an anionic polymer as an example. A carboxyl group possessed by a general anionic polymer flocculant is present in the following equilibrium state in water. Under the acidic region, the equilibrium moves to the left and the dissociation of the carboxyl group is suppressed. In other words, when the aqueous polymer flocculant solution is acidified, the carboxyl group of the anionic polymer is in an undissociated state in the aqueous solution, and when added to high-concentration salt water as it is, divalent ions ( (Mg, Ca, etc.) can be suppressed, and aggregates are not formed instantaneously. Therefore, the polymer flocculant that aggregates before trapping (trapping) the target impurities can be reduced as much as possible, which is desirable because it is considered that the drug can be reduced and the cost can be reduced.

  FIG. 1 is an overall configuration diagram of a water treatment apparatus having a coagulation treatment unit according to the present invention. In the following, the case of a seawater desalination apparatus will be described as an example of the water treatment apparatus. However, the present invention is not limited to this, and the present invention is similarly applied to sewage treatment apparatuses such as industrial wastewater treatment equipment and domestic wastewater. Is. In FIG. 1, the flow of water is indicated by solid arrows, and the signal line (control line) is indicated by a dotted line.

  As shown in FIG. 1, the water treatment apparatus of the present invention includes a flocculant aqueous solution storage tank 1, a first water quality inspection unit 7 that measures the quality of seawater that is treated water, and a polymer flocculant that is treated water. A coagulation tank 11 for adding an aqueous solution to perform coagulation treatment, a filtration unit 9 for separating and removing aggregates from the treated water after the coagulation reaction, and a second method for measuring water quality of the water to be treated after the aggregates are removed. The water quality inspection unit 8 includes a reverse osmosis membrane unit (hereinafter, RO membrane unit) 10 that removes salt from the water to be treated from which aggregates have been removed, and a control unit 60 that controls them. The RO membrane unit 10 removes ions such as chloride ions and sodium ions from the water to be treated from which the aggregates have been removed. The filtration unit 9 is, for example, any one of a precipitation tank (precipitation part), an ultrafiltration part, a microfiltration part, a sand filtration tank (sand filtration part), a multimedia filter filtration part, or a combination thereof. Configured appropriately. And the filtration part 9 isolate | separates and removes the aggregate produced | generated when the impurity in to-be-processed water is capture | acquired by the coagulant | flocculant in the coagulation tank 11. In the overall configuration of the water treatment apparatus shown in FIG. 1, the configuration excluding the RO membrane unit 10 is referred to as an aggregating treatment apparatus.

  The flocculant aqueous solution storage tank 1 is provided with a stirrer 5 for stirring the polymer flocculant aqueous solution, a branch channel 20 for measuring the particle size distribution, and a particle size distribution of the polymer flocculant aqueous solution provided in the branch channel 20. A particle size distribution measuring device 50 is provided. The particle size distribution measuring device 50 includes a flow cell 2 for flowing a polymer flocculant aqueous solution, a laser irradiation unit 3 for irradiating a polymer flocculant aqueous solution flowing in the flow cell 2 with a laser, and a laser irradiation unit 3 sandwiching the flow cell 2. It is comprised from the detection part 4 arrange | positioned so that it may oppose. The detection unit 4 detects scattered light intensity by receiving and photoelectrically converting scattered light generated by irradiating the flocculant in the polymer flocculant aqueous solution with a laser. Then, the detection unit 4 obtains the particle size distribution of the flocculant in the polymer flocculant aqueous solution based on the scattered light intensity distribution, and outputs it to the flocculant addition rate control unit 6. Thereby, the flocculant addition rate control unit 6 acquires the median diameter (d50) in the particle size distribution of the polymer flocculant aqueous solution in the flocculant aqueous solution storage tank 1.

  Here, the case where the particle size distribution measuring apparatus 50 measures the particle size distribution by the dynamic light scattering method in the flow cell 2, the laser irradiation unit 3 and the detection unit 4 has been described. Particle size distribution measurement methods such as diffraction method, image imaging method, and gravity sedimentation method are known. In the laser diffraction method, the particle diameter is obtained from the intensity distribution of diffracted light and scattered light obtained by irradiating a particle with laser. Image imaging is a method in which an image of a particle is obtained with an optical microscope or an electron microscope, and the size of the particle is obtained from the image. Gravity sedimentation is a method in which an analytical sample is uniformly dispersed in a solvent. The particle size distribution is obtained from the sedimentation rate of the particles. Moreover, in this invention, although the particle size distribution measuring apparatus 50 was comprised by the flow cell 2, the laser irradiation part 3, and the detection part 4, it is not restricted to this. For example, the particle size distribution measuring device 50 may be configured from a laser irradiation fiber and a light receiving fiber disposed so as to be orthogonal to the laser irradiation fiber, and installed in the flocculant aqueous solution storage tank 1. In this case, it is not necessary to provide the branch channel 20 in the flocculant aqueous solution storage tank 1.

  Moreover, in FIG. 1, the agitation tank 11 is provided with a stirrer 12, and the speed of the stirring blade can be controlled by controlling the number of rotations of the motor. That is, the stirring intensity can be controlled. Here, the stirring strength is determined by the capacity of the agglomeration tank, the area of the stirring blade, the rotational speed of the stirring blade (stirring speed), etc., but since the capacity and the area of the stirring blade are constant, the rotational speed of the stirring blade is controlled. Thus, the stirring intensity is controlled.

  Next, the operation of the water treatment apparatus shown in FIG. 1 will be described. First, the quality of the treated water taken is measured by the first water quality inspection unit 7. Here, examples of water quality to be measured include total organic carbon (TOC) concentration, water temperature, pH, and turbidity. At this time, the particle size distribution of the polymer flocculant aqueous solution stored in the flocculant aqueous solution storage tank 1 is measured by the particle size distribution measuring device 50. Subsequently, after the water to be treated is drawn into the coagulation tank 11, the coagulant is added based on the water quality data of the water measured by the first water quality inspection unit 7 and the particle size distribution data of the polymer flocculant aqueous solution. The rate control unit 6 controls the pump 13 to add an optimal amount of the polymer flocculant aqueous solution from the flocculant aqueous solution storage tank 1 to the flocculant tank 11 (feed forward control). After sufficiently allowing the polymer flocculant to act on the stirrer 12 in the agglomeration tank 11, the agglomerate is removed by the filtration unit 9. Thereafter, the quality of the treated water after the aggregate is removed is measured by the second water quality inspection unit 8. The flocculant addition rate control unit 6 is configured to provide a highly accurate and optimum polymer flocculant aqueous solution by feedback control based on the water quality data measured by the second water quality inspection unit 8 and the particle size distribution data of the polymer flocculant aqueous solution. Determine the addition amount and add to the water to be treated. The coagulant addition rate control unit 6 stores in advance a relationship between water quality data, particle size distribution data of the coagulant aqueous solution, and the optimum addition amount of the coagulant in a storage unit (not shown). More preferably, the flocculant aqueous solution storage tank 1 is provided with a pH measurement mechanism for monitoring and controlling the pH of the polymer flocculant aqueous solution and a mechanism capable of adding a pH adjuster.

  The polymer flocculant aqueous solution stored in the flocculant aqueous solution storage tank 1 includes a polyacrylamide flocculant, a polysulfonic acid flocculant, a polyacrylic flocculant, a polyacrylic ester flocculant, Either a polyamine flocculant or a polymethacrylic acid flocculant can be used. In particular, a polymer having a carboxyl group with a small acid dissociation constant has a low ionization rate when added to seawater, and thus can capture impurities more effectively.

  Here, a mechanism for capturing impurities in the water to be treated by the polymer flocculant will be described. FIG. 5 is a diagram for explaining the relationship between the particle size distribution and the trapping of impurities.

  In FIG. 5, when the median diameter (d50) in the particle size distribution in the polymer flocculant aqueous solution is small, the polymer flocculant dissolves sufficiently uniformly, and each polymer chain is independently agglomerated tank. 11 to be added to the water to be treated. On the other hand, when the median diameter (d50) is large, the polymer flocculant is not sufficiently dissolved, and an aggregate is formed by entanglement of the polymer flocculant molecules and the like. Will be added to the water. In FIG. 5, when the median diameter (d50) is small compared to the case where the median diameter (d50) is large, it is possible to act on many impurities in the water to be treated by trapping impurities in the water to be treated with one polymer chain. Efficient coagulation treatment is possible. Therefore, high efficiency of the aggregation treatment can be realized by measuring the particle size distribution of the aqueous polymer flocculant solution and performing the aggregation treatment while confirming that the particle size distribution is appropriate. Thereby, merits such as reduction of the drug amount by optimizing the addition rate of the flocculant and reduction of the risk of harmful effects due to excessive addition of the drug can be obtained.

  In the above description, the polymer flocculant has been described. The same applies to the inorganic flocculant. If the median diameter (d50) of the flocculant aqueous solution is large, the inorganic flocculant is not ionized and added to the water to be treated. It is considered that aggregates and aggregates have been formed before, and this is thought to lead to reduced effects when added to the water to be treated. Therefore, for example, when two types of inorganic flocculants and polymer flocculants are used as flocculants, it is desirable to measure the particle size distribution of the aqueous solution for both these inorganic flocculants and polymer flocculants. In particular, the effect of the polymer flocculant is significant, so the effect is great.

  Here, the case where an anionic polymer flocculant is applied is demonstrated regarding the case where a polymer flocculant is applied to high concentration salt water. When the carboxyl group is added in a dissociated state as in Formula 1, it is instantaneously bound by electrostatic interaction with microfloc, Mg, Ca, etc. in seawater, which is high-concentration saltwater, to form an aggregate. On the other hand, when the pH of the aqueous solution of the anionic polymer flocculant is lowered, the equilibrium in Formula 1 is biased to the right and the carboxyl group is not dissociated and is added to seawater. In that case, unlike the above, there is a time lag from the addition of the flocculant to the formation of the aggregate, and the anionic polymer can physically capture more micro flocs during that time. Therefore, the efficiency of the flocculant can be improved by lowering the pH of the aqueous solution containing the anionic polymer flocculant. Furthermore, when the steady state is reached, since the equilibrium constant of Formula 1 is determined by the pH of the water to be treated, the pH of the water to be treated also affects the agglomeration efficiency. If a pH adjuster is also added, aggregates can be formed more effectively.

  In the configuration shown in FIG. 1, the quality of the water to be treated (seawater) taken by the first water quality inspection unit 7 is measured, and the quality of the treated water after removing the aggregates is measured by the second water quality inspection unit 8. Although it is configured, water quality measurement will be described here.

By sensing substances (total organic carbon (TOC) and turbidity) contained in the treated water taken, water quality information (water quality data) and treated water quality data are obtained. Feedback and feedforward control are performed using the water quality data measured by the first water quality inspection unit 7 and the second water quality inspection unit 8. The flocculant addition rate control unit 6 determines the addition amount of various flocculants suitable for the quality of the water to be treated (water quality data measured by the first water quality inspection unit 7). As a result, the maximum flocculant efficiency can be realized by optimizing the amount of flocculant added, it is possible to prevent excessive flocculant addition and unnecessary sludge generation, and optimize the operating cost of the water treatment plant Can do.
In addition to the above, the water quality data to be measured includes water temperature, pH, conductivity, protein, saccharides (neutral sugars, acidic sugars), adenosine triphosphate (ATP) activity, etc. If it is an index considered to influence the fouling (clogging) of the RO membrane unit 10 by the component and the inorganic component, it is preferable to include in the water quality data to be measured.

  In FIG. 1, the first water quality inspection unit 7 and the second water quality inspection unit 8 are arranged in the front stage of the coagulation tank 11 and the rear stage of the filtration unit 9, respectively. In order to carry out with high accuracy, it is also possible to simply arrange one of the water quality inspection sections to perform water quality evaluation and control of the flocculant addition rate.

  The flocculant addition rate control unit 6 determines the amount of the polymer flocculant aqueous solution added to the water to be treated in the flocculence tank 11, and the polymer flocculant aqueous solution stored in the flocculant aqueous solution storage tank 1. The stirring strength of the stirrer 5 provided in the flocculant aqueous solution storage tank 1 is controlled so that the median diameter (d50), which is the diameter distribution, is 1.0 μm or less. Here, as described above, the stirring strength is determined by the capacity of the tank, the area of the stirring blade, the rotation speed of the stirring blade (stirring speed), etc., but the capacity and the area of the stirring blade are constant. The stirring intensity is controlled by controlling the rotation speed.

Next, a water treatment apparatus when two types of flocculants are used in combination will be described. FIG. 2 is another overall configuration diagram of a water treatment apparatus having a coagulation treatment unit according to the present invention. Constituent elements similar to those in FIG. 1 further includes a first flocculant aqueous solution storage tank 31 for storing an inorganic flocculant aqueous solution in the water treatment apparatus described above, and a flocculant tank 21 for adding an inorganic flocculant aqueous solution to the water to be treated and performing a flocculant treatment. The configuration is provided. Hereinafter, the aggregating tank 21 to which the inorganic aggregating agent aqueous solution is added to perform the aggregating process is referred to as a first aggregating tank, and the aggregating tank 11 to which the polymer aggregating agent aqueous solution is added to perform the aggregating process is referred to as a second aggregating tank. As the inorganic flocculant, for example, any one of sulfuric acid band, ferric chloride, ferric sulfate, aluminum chloride, aluminum sulfate, polyaluminum chloride, and the like is used.

  In the configuration of the water treatment apparatus shown in FIG. 2, both the first flocculant aqueous solution storage tank 31 for storing the inorganic flocculant aqueous solution and the second flocculant aqueous solution storage tank 1 for storing the polymer flocculant aqueous solution, Although it is desirable to provide the particle size distribution measuring device 50, here, only the second flocculant aqueous solution storage tank 1 is provided. The operation of the water treatment device shown in FIG. 2 will be described. An inorganic flocculant aqueous solution stored in the first flocculant aqueous solution storage tank 31 is added to the first flocculant tank 21 via the pump 14. In addition, a polymer flocculant aqueous solution stored in the second flocculant aqueous solution storage tank 1 is added to the second flocculant tank 11 connected to the subsequent stage of the first flocculant tank 21 via the pump 13. . The first agglomeration tank 21 and the second agglomeration tank 11 are each provided with a stirrer 22 and a stirrer 12, and the speed of the stirring blades can be controlled by controlling the number of rotations of the motor. Here, the first flocculant aqueous solution storage tank 31 and the second flocculant storage tank 1 include an inorganic flocculant aqueous solution and a polymer in a state where the median diameter (d50) in the particle size distribution is 1.0 μm or less. Each of the flocculant aqueous solutions is stored.

  When the inorganic flocculant aqueous solution is added to the first flocculent tank 21, rapid stirring is performed for a predetermined time by the stirrer 22, and the water to be treated after adding the inorganic flocculant aqueous solution and stirring for the predetermined time is the second stage in the latter stage. The water is fed to the coagulation tank 11. Thereafter, the polymer flocculant aqueous solution is added to the water to be treated in the second flocculation tank 11 and is stirred gently by the stirrer 12 for a predetermined time. The water to be treated that has been gently stirred for a predetermined time is sent to the filtration unit 9 where the aggregates formed in the water to be treated are separated and removed, and the RO membrane unit 10 performs membrane separation into concentrated water and fresh water. In this way, by rapidly stirring in the first flocculation tank 21 and slowly stirring in the second flocculation tank 11, the particle size of flocs that are aggregates in the water to be treated can be increased, and the flocculation performance can be improved. It becomes possible to improve. The addition amount of the inorganic flocculant aqueous solution and the addition amount of the polymer flocculant aqueous solution are the water quality data from the first water quality inspection unit 7 and the water quality data from the second water quality inspection unit 8 as in FIG. And the median diameter (d50) in the particle size distribution in the polymer flocculant aqueous solution from the particle size distribution measuring device 50.

  Next, a configuration using a system in which a flocculant is mixed in-line, instead of the agglomeration tank shown in FIGS. 1 and 2 will be described. FIG. 3 is another overall configuration diagram of a water treatment apparatus having an aggregation treatment unit according to the present invention. In the water treatment apparatus shown in FIG. 3, an in-line mixer 101 is arranged in place of the flocculation tank 11 and the stirrer 12 shown in FIG. 1, and the polymer flocculant aqueous solution is supplied to the water to be treated through the pump 13 in the previous stage of the in-line mixer 101. It is set as the structure to add. Specifically, a port that can inject the polymer flocculant aqueous solution is provided in a pipe connected to the inflow portion of the in-line mixer 101. The inline mixer 101 includes, for example, two spiral partition walls facing each other. The two spiral partition walls facing each other cause a shear stress to act on the water to be treated flowing inside, and the polymer flocculant and impurities contained in the water to be treated are mixed to form an aggregate. It forms a flock. As in FIG. 1, the flocculant addition rate control unit 6 performs the polymer aggregation obtained from the water quality data from the first water quality inspection unit 7, the water quality data from the second water quality detection unit 8, and the particle size distribution measuring device 50. The addition amount of the polymer flocculant aqueous solution is determined based on the median diameter (d50) in the particle size distribution in the agent aqueous solution. Thus, when using the in-line mixer 101, it is necessary to set the pipe length or the pipe diameter in order to secure the reaction time after mixing, that is, the time for the polymer flocculant to capture impurities in the water to be treated. is there.

  Moreover, FIG. 4 is another whole block diagram of the water treatment apparatus which has the aggregation process part which concerns on this invention. In the water treatment apparatus shown in FIG. 4, an inline mixer 102 and an inline mixer 101 are provided in place of the first flocculation tank 21 and the stirrer 22 and the second flocculation tank 11 and the stirrer 12 shown in FIG. Since the structure of the inline mixer itself is the same as that shown in FIG. In the configuration shown in FIG. 4, the aqueous inorganic flocculant solution is added to the water to be treated through the pump 14 before the in-line mixer 102, and the pump 13 is connected to the piping section connecting the in-line mixer 102 and the in-line mixer 101. A polymer flocculant aqueous solution is added to the water to be treated. The addition amount of the inorganic flocculant aqueous solution and the addition amount of the polymer flocculant aqueous solution are determined by the flocculant addition rate control unit 6 as in FIG. Moreover, in order to ensure the reaction time after mixing, it is necessary to set a pipe length or a pipe diameter similarly to the structure shown in FIG.

According to the above-described water treatment apparatus of the present invention shown in FIGS. 1 to 4, the median diameter (d50) in the particle size distribution in the flocculant aqueous solution can be stored at 1.0 μm or less, and the efficiency of the coagulation treatment is improved. Is possible. In addition, optimization of the flocculant addition rate can achieve maximum flocculant efficiency, making it possible to prevent excessive flocculant addition and unnecessary sludge generation, and to optimize the operating costs of water treatment equipment. it can.
The flocculant aqueous solution storage tanks 1 and 31 used in the water treatment apparatus of the present invention shown in FIGS. 1 to 4 are not particularly limited in shape and material as long as the flocculant can be stored. Further, since the pH of the flocculant aqueous solution also affects the efficiency of the flocculation treatment, it is desirable to have a pH measurement mechanism and a pH adjuster addition mechanism.

  Examples of the present invention will be specifically described below together with comparative examples.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the vessel, a 0.1% polyacrylic acid polyacrylamide copolymer aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by setting the pH to 5.1, the particle size distribution (d50) in the polymer flocculant aqueous solution to 1.0 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.5 TOC / ppm and an acid sugar removal rate of 80% were obtained as the treated water quality.

  At this time, as Comparative Example 1, when the particle size distribution (d50) in the polymer flocculant aqueous solution was changed to 3.0 μm and the other conditions were the same, the treated water quality was 0.6 TOC / ppm, acid sugar removal A rate of 40% was obtained.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the vessel, a 0.1% polyacrylic acid polyacrylamide copolymer aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by setting the pH to 5.1, the particle size distribution (d50) in the polymer flocculant aqueous solution to 0.7 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.5 TOC / ppm and an acid sugar removal rate of 82% were obtained as the treated water quality.

  At this time, as Comparative Example 2, when the particle size distribution (d50) in the polymer flocculant aqueous solution was changed to 1.5 μm and the other conditions were the same, the treated water quality was 0.6 TOC / ppm, acid sugar removal. A rate of 55% was obtained.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the vessel, a 0.1% polyacrylic acid polyacrylamide copolymer aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by adjusting the pH to 5.1, the particle size distribution (d50) in the polymer flocculant aqueous solution to 0.3 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.4 TOC / ppm and acidic sugar removal rate of 85% were obtained as treated water quality.

  At this time, as Comparative Example 3, when the particle size distribution (d50) in the polymer flocculant aqueous solution was changed to 1.1 μm and other conditions were the same, the treated water quality was 0.5 TOC / ppm, acid sugar removal A rate of 72% was obtained.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the solution, a 0.1% concentration polyacrylic acid aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by setting the pH to 3.7, the particle size distribution (d50) in the polymer flocculant aqueous solution to 1.0 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.5 TOC / ppm and an acid sugar removal rate of 82% were obtained as the treated water quality.

  At this time, as Comparative Example 4, when the particle size distribution (d50) in the polymer flocculant aqueous solution was changed to 3.0 μm and the other conditions were the same, the treated water quality was 0.6 TOC / ppm, acid sugar removal A rate of 42% was obtained.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the solution, a 0.1% concentration polyacrylic acid aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by setting the pH to 3.7, the particle size distribution (d50) in the polymer flocculant aqueous solution to 0.7 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.4 TOC / ppm and an acid sugar removal rate of 86% were obtained as treated water quality.

  At this time, as Comparative Example 5, when the particle size distribution (d50) in the polymer flocculant aqueous solution was changed to 1.5 μm and other conditions were the same, the treated water quality was 0.6 TOC / ppm, acid sugar removal A rate of 59% was obtained.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the solution, a 0.1% concentration polyacrylic acid aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by setting the pH to 3.7, the particle size distribution (d50) in the polymer flocculant aqueous solution to 0.3 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.4 TOC / ppm and an acid sugar removal rate of 90% were obtained as the treated water quality.

  At this time, as Comparative Example 6, when the particle size distribution (d50) in the polymer flocculant aqueous solution was changed to 1.1 μm and the other conditions were the same, the treated water quality was 0.5 TOC / ppm, acid sugar removal A rate of 75% was obtained.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the vessel, a 0.1% polyacrylic acid polyacrylamide copolymer aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by setting the pH to 1.0, the particle size distribution (d50) in the polymer flocculant aqueous solution to 1.0 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.5 TOC / ppm and an acid sugar removal rate of 83% were obtained as treated water quality.

  At this time, as Comparative Example 7, when the pH was changed to 8.0 and the other conditions were the same, 0.6 TOC / ppm and an acidic sugar removal rate of 45% were obtained as the treated water quality.

  In this embodiment, using the configuration of the water treatment apparatus shown in FIG. 2, a 3.8% iron chloride aqueous solution is used as the inorganic flocculant aqueous solution stored in the flocculant aqueous solution storage tank 31. As the polymer flocculant aqueous solution stored in the solution, a 0.1% concentration polyacrylic acid aqueous solution was used. The water to be treated was seawater, and a sand filtration tank capable of removing impurities having a pore diameter of about 5 μm was used as the filtration unit 9. In order to verify the effect of the agglomeration treatment by setting the pH to 1.0, the particle size distribution (d50) in the polymer flocculant aqueous solution to 1.0 μm, and collecting the treated water after sand filtration, Carbon concentration (TOC) and acid sugar concentration were evaluated. As a result of the evaluation, 0.4 TOC / ppm and an acid sugar removal rate of 86% were obtained as treated water quality.

  At this time, as Comparative Example 8, when the pH was changed to 8.0 and the other conditions were the same, 0.6 TOC / ppm and an acidic sugar removal rate of 51% were obtained as treated water quality.

  As mentioned above, Example 1 to Example 8 and Comparative Example 1 to Comparative Example 8 are summarized. FIG. 6 is a diagram for explaining the relationship between the particle size distribution of each example and the treated water quality, and FIG. 7 is a diagram for explaining the relationship between the particle size distribution of each comparative example and the treated water quality.

  6 and 7, Example 1 and Comparative Example 3 were examined when a 0.1% polyacrylic acid polyacrylamide copolymer aqueous solution was used as the polymer flocculant aqueous solution and the pH was 5.1. To do. In Example 1, the particle size distribution (d50) is 1.0 μm and the treated water quality is 0.5 TOC / ppm, and the acid sugar removal rate is 80%. In Comparative Example 3, the particle size distribution (d50) is 1. The treated water quality at 1 μm is 0.5 TOC / ppm, and the acid sugar removal rate is 72%. That is, TOC shows the same value, and only the acid sugar removal rate shows different values between 80% and 72%.

  Similarly, Example 4 and Comparative Example 6 in which a polyacrylic acid aqueous solution having a concentration of 0.1% is used as the polymer flocculant aqueous solution and the pH is 3.7 are examined. In Example 4, the particle size distribution (d50) is 1.0 μm and the treated water quality is 0.5 TOC / ppm, and the acid sugar removal rate is 82%. In Comparative Example 6, the particle size distribution (d50) is 1. The treated water quality at 1 μm is 0.5 TOC / ppm, and the acid sugar removal rate is 75%. TOC shows the same value, and only the acid sugar removal rate shows different values between 82% and 72%.

  Here, when paying attention to the acid sugar removal rate, when operating the water treatment apparatus shown in FIG. 2 which is one of the embodiments of the present invention, the RO installed in the subsequent stage of the second flocculation tank 11 and the filtration unit 9. It was found that the load on the membrane unit 10 changes greatly with the acidic sugar removal rate of 80% as a boundary. That is, the rate of change in the clogging rate (filtration pressure increase) rate of the membrane correlates with the acidic sugar removal rate, and changes greatly with the acidic sugar removal rate of 80% as a boundary. FIG. 8 is a diagram showing the relationship between the acid sugar removal rate and the clogging (filtration pressure) increase rate. The treated water having different acid sugar removal rates is passed through the RO membrane unit 10 and the clogging (filtration pressure) increase rate at that time is acquired and plotted in FIG. As shown in FIG. 8, when the acid sugar removal rate is less than 80%, the clogging rate is high and the rate of change A is small. On the other hand, when the acid sugar removal rate is 80% or more, the clogging rate is rapidly reduced and the rate of change B is greater than the rate of change A. That is, the clogging suppression effect in the RO membrane unit 10 becomes remarkable by setting the acid sugar removal rate to 80% or more. This shows that a high clogging suppression effect can be obtained by setting the median diameter (d50) in the particle size distribution of the flocculant aqueous solution to 1.0 μm or less.

  Further, assuming the case where the polymer flocculant is completely dissolved, the lower limit of the median diameter (d50) in the particle size distribution of the flocculant aqueous solution is set. That is, the atoms constituting the polymer flocculant are three elements of C, H, and O, and by calculating the length of the polymer and the occupied volume from these covalent bond radii, the lower limit median diameter is 1.4 nm. Is obtained. Therefore, the median diameter in the particle size distribution of the aqueous polymer flocculant solution used in the present invention is preferably 1.4 nm or more and 1.0 μm or less.

  Further, when Example 1 is compared with Example 7, the median diameter (d50) in the particle size distribution of the polymer flocculant aqueous solution is 1.0 μm, which is the same, and only pH is 5.1 in Example 1, Example 7 Then it is 1.0. These treated water qualities are 0.5 TOC / ppm in Example 1 and an acid sugar removal rate of 80%, whereas in Example 7, the water content is 0.5 TOC / ppm and an acid sugar removal rate of 83%.

  Further, when Example 4 and Example 8 are compared, the median diameter (d50) in the particle size distribution of the polymer flocculant aqueous solution is 1.0 μm and the same, and only the pH is 3.7 in Example 4 and in Example 8. It is set to 1.0. These treated water qualities are 0.5 TOC / ppm in Example 4 and an acid sugar removal rate of 82%, whereas in Example 8, they are 0.4 TOC / ppm and an acid sugar removal rate of 86%.

  From the above, by setting the median diameter (d50) in the particle size distribution of the polymer flocculant aqueous solution used in the present invention to 1.0 μm or less, the clogging suppressing effect in the RO membrane unit 10 installed in the latter stage as described above can be obtained. Furthermore, by reducing the pH of the polymer flocculant aqueous solution (in an acidic state), the acidic sugar removal rate can be further improved, and the clogging suppressing effect can be further improved. In addition, it is preferable to add a pH adjuster so that pH may be adjusted to 1.0 or less.

  In addition, this invention is not limited to the structure of above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of a certain example can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Moreover, it is possible to add / delete / replace the configuration of the other embodiment with respect to a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Flocculant aqueous solution storage tank 2 Flow cell 3 Laser irradiation part 4 Detection part 5 Stirrer 6 Flocculant addition rate control part 7 1st water quality inspection part 8 2nd water quality inspection part 9 Filtration part 10 RO membrane unit 11 Coagulation tank 20 grain Branch channel 50 for diameter distribution measurement Particle size distribution measuring apparatus 101 In-line mixer

Claims (17)

A flocculation treatment method of adding one or more kinds of flocculant aqueous solutions to water to be treated containing impurities to form agglomerates and removing the impurities,
The median diameter in the particle size distribution of said flocculant aqueous solution is 1.0 micrometer or less, The aggregation processing method characterized by the above-mentioned. In the aggregation treatment method according to claim 1,
An inorganic flocculant aqueous solution is added to the treated water to form an aggregate,
A coagulation treatment method comprising adding an aqueous polymer coagulant solution to the water to be treated after the formation of the aggregate. In the aggregation treatment method according to claim 2,
The median diameter in the particle size distribution of the polymer flocculant aqueous solution is in the range of not less than 1.4 nm and not more than 1.0 μm. In the aggregation treatment method according to claim 1,
The flocculant aqueous solution is adjusted to have a pH of 1.0 or less. In the aggregation processing method according to any one of claims 1 to 3,
The amount of the flocculant aqueous solution added is determined based on water quality data of the water to be treated and a median diameter in a particle size distribution of the flocculant aqueous solution. In the aggregation processing method according to claim 2 or 3,
The inorganic coagulant aqueous solution is any one of sulfuric acid band, ferric chloride, ferric sulfate, aluminum chloride, aluminum sulfate and polyaluminum chloride. In the aggregation processing method according to claim 2 or 3,
The polymer flocculant aqueous solution includes any of polyacrylamide flocculants, polysulfonic acid flocculants, polyacrylic flocculants, polyacrylate flocculants, polyamine flocculants, and methacrylic flocculants. A coagulation treatment method characterized by the above. In the aggregating treatment method according to claim 5,
The water quality data of the water to be treated includes at least total organic carbon (TOC), turbidity, water temperature, pH, conductivity, protein, saccharide (neutral sugar, acidic sugar), and adenosine triphosphate (ATP) activity. A coagulation treatment method, comprising: A flocculant aqueous solution storage tank that has a stirrer and stores the flocculant aqueous solution;
A particle size distribution measuring device for measuring the particle size distribution of the flocculant aqueous solution in the flocculant aqueous solution storage tank;
A coagulation tank for mixing the water to be treated and the aqueous flocculant solution to be added to form an aggregate;
An aggregate removal unit for removing the aggregate from the treated water containing the aggregate;
An aggregating apparatus comprising: a control unit that controls the agitator so that a median diameter in the particle size distribution of the aqueous flocculant solution is 1.0 μm or less based on a measured particle size distribution. The aggregation processing apparatus according to claim 9, wherein
The flocculant aqueous solution is an aqueous solution of an anionic polymer flocculant. The aggregation processing apparatus according to claim 9, wherein
A water quality inspection unit for measuring the quality of the treated water;
The control unit determines the amount of the flocculant aqueous solution added to the water to be treated based on the measured water quality of the water to be treated and the particle size distribution from the particle size distribution measuring device. apparatus. The aggregation processing apparatus according to claim 11,
A first water quality inspection unit for measuring the quality of the treated water;
A second water quality inspection unit that measures the quality of the treated water from which the aggregates have been removed,
The control unit determines an addition amount of the flocculant aqueous solution to the water to be treated based on measurement results from the first water quality inspection unit, the second water quality inspection unit, and the particle size distribution measuring device. An aggregating apparatus characterized by the above. In the aggregating apparatus according to claim 9 or 11,
The flocculant aqueous solution storage tank is composed of a first storage tank for storing an inorganic flocculant aqueous solution and a second storage tank for storing a polymer flocculant aqueous solution,
The agglomeration tank is
A first flocculating tank for mixing the inorganic flocculant aqueous solution from the first storage tank and the water to be treated;
2nd which arrange | positions in the back | latter stage of the said 1st coagulation tank, mixes the to-be-processed water containing the aggregate introduced from the said 1st coagulation tank, and the polymer flocculant aqueous solution from the said 2nd storage tank. An aggregating apparatus comprising an aggregating tank. A flocculant aqueous solution storage tank that has a stirrer and stores the flocculant aqueous solution;
A particle size distribution measuring device for measuring the particle size distribution of the flocculant aqueous solution in the flocculant aqueous solution storage tank;
A coagulation tank for mixing the water to be treated and the aqueous flocculant solution to be added to form an aggregate;
An aggregate removal unit for removing the aggregate from the treated water containing the aggregate;
A separation unit that performs a membrane separation process on the treated water from the aggregate removal unit;
A water treatment apparatus comprising: a control unit that controls the agitator so that a median diameter in a particle size distribution of the flocculant aqueous solution is 1.0 μm or less based on a measured particle size distribution. The water treatment device according to claim 14, wherein
The treated water is seawater, and the flocculant aqueous solution is an aqueous solution of an anionic polymer flocculant,
The separation unit includes a reverse osmosis membrane (RO membrane), and the reverse osmosis membrane separates concentrated water and fresh water having a high salinity. The water treatment device according to claim 14, wherein
The said control part controls the stirring speed of the said stirrer so that the median diameter in the particle size distribution of the said coagulant | flocculant aqueous solution may be 1.0 micrometer or less. The water treatment device according to claim 15, wherein
A water treatment apparatus, wherein a pH adjuster is added so that the pH of the flocculant aqueous solution in the flocculant aqueous solution storage tank is 1.0 or less.

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